Edm electrode construction and method of making same

ABSTRACT

An electrode construction for use in operative association with electrical discharge machines, and method of making same, the electrode comprising a plurality of adjacently oriented cooperable segmental electrode sections arranged so as to define a working surface having a conformation corresponding to the shape to which a workpiece is to be machined; a support structure or holder member adapted to operatively support the electrode sections in a manner such that said sections may be removed and replaced after they have become excessively eroded or otherwise consumed; the method of making the electrode including the steps of providing a mold or form having a face portion of the same conformation as the ultimate shape to which the workpiece is to be machined; providing a parting or release substance on the face portion of the form and thereafter arranging the plurality of electrode sections on the form; providing a deformable material on one side of the holder member and biasing said member toward and into engagement with the electrode sections in a manner such that the material is deformed so as to define a reference surface upon which the electrode sections may be detachably mounted.

United States Patent 2,861,164 11/1958 Stegler 3,058,895 10/1962Williams Lloyd A. Schroeder Southfield, Mich. 822,892

May 8, 1969 June 8, I97 1 Automotive Pattern Co. Detroit, Mich.

Inventor Appl. No. Filed Patented Assignee EDM ELECTRODE CONSTRUCTIONAND METHOD OF MAKING SAME 22 Clalms, 8 Drawing Elgs.

References Cited UNITED STATES PATENTS 2l9/69(E) 219/69(E) PrimaryExaminer-J. V. Truhe Assistant Examiner-Hugh D. JaegerAttarneyl-larness, Dickey & Pierce ABSTRACT: An electrode constructionfor use in operative association with electrical discharge machines, andmethod of making same, the electrode comprising a plurality ofadjacently oriented cooperable segmental electrode sections arranged soas to define a working surface having a conformation corresponding tothe shape to which a workpiece is to be machined; a support structure orholder member adapted to operatively support the electrode sections in amanner such that said sections may be removed and replaced after theyhave become excessively eroded or otherwise consumed; the method ofmaking the electrode including the steps of providing a mold or formhaving a face portion of the same conformation as the ultimate shape towhich the workpiece is to be machined; providing a parting or releasesubstance on the face portion of the form and thereafter arranging theplurality of electrode sections on the form; providing a deformablematerial on one side of the holder member and biasing said member towardand into engagement with the electrode sections in a manner such thatthe material is deformed so as to define a reference surface upon whichthe electrode sections v may be detachably mounted.

EDM ELECTRODE CONSTRUCTION AND METHOD OF MAKING SAME BACKGROUND OF THEINVENTION In electrical discharge machining, the tooling portion of theelectrode is provided with a working face having a configuration towhich a metal workpiece is to be conformed. The electrode andworkpieceare associated with an electrical circuit which includes anelectrical power source. When the working face of the electrode and theselected surface of the workpiece to be machined are brought into apredetermined spaced relationship in the presence of a dielectricmedium, a series of electrical sparks are discharged across the gapbetween the working face of the electrode and the surface of theworkpiece. These electrical sparks erode the metal of the workpiece,thereby machining or shaping the surface thereof into confonnance withthe working face of the electrode. The dielectric fluid is circulatedbetween and around the working face of the electrode and the machinedsurface of the workpiece to prevent overheating of either the electrodeor the workpiece, and to carry away the metal particles machined fromthe workpiece.

One of the problems posed in EDM machining is that, although theelectrical sparks or discharges remove or erode metal particles from theworkpiece, they also erode the working face of the electrode so thatsaid face is eventually destroyed or seriously impaired. It has been theusual practice to individually machine the working face of eachelectrode to arrive at the preselected conformation thereof. In mostcases, the tooling or face portion is an integral part of the electrodebody, with the result that the entire electrode must be frequentlyreplaced during the machining of a workpiece after such time as theeffectiveness of the working face of the electrode has been sufficientlyimpaired.

It will be apparent that when the working face of the electrode is of arelatively complex configuration, i.e., three dimensional,nondevelopable, etc., the electrode will be relatively expensive tomanufacture, since a substantial amount of machining and hence finishingis required. Since such an electrode, for all practical purposes, has arelatively short working life, the necessity for individually machiningreplacement electrodes contributes greatly to the overall cost ofelectrical discharge machining operations. Moreover, while electrodesmade of certain exotic" metals, such as tungsten and the like arecapable of relatively long use, such electrodes are extremely difficultto produce and are relatively expensive.

The present invention is intended to overcome and obviate the variousobjectionable characteristics hereinabove stated 1 with regard to EDMelectrodes through the provision of a novel electrode construction, andmethod of making same, which utilizes certain expendable and reusableparts. More particularly, the present invention provides a new andimproved electrode construction comprising a plurality of segmentalelectrode sections which are fabricated of an expendable conductivematerial and are adapted to be mounted on a permanently formed reusableelectrode holder for positioning the electrode sections and operativelysupporting the same in an associated electrical discharge machine. Theassociated electrode holder is fabricated in a manner such that itdefines a reference surface or face upon which the electrode sectionsare detachably secured, with the result that when certain electrodesections are removed for purposes of replacement, successive electrodesections may be mounted upon the reference face and thereby beaccurately positioned with respect to one another so as to'define aprecision working face adapted to perform a machining operation onpreselected surfaces of workpieces subjected to the operation of theelectrical discharge machine, as will hereinafter be described indetail.

SUMMARY OF THE INVENTION This invention relates generally to electricaldischargemachining devices and, more particularly, to a new and improvedelectrical discharge machining electrode and method of making the same.

It is accordingly a general object of the present invention to provide anew and improved electrode construction for electrical dischargemachines.

It is another general object of the present invention to provide a newand improved method of manufacturing electrodes for the aforesaidapplications.

It is a more particular object of the present invention to provide a newand improved composite electrical discharge machine electrode having areusable support member adapted to detachably and operatively support aplurality of replaceable or expendable segmental electrode sections.

It is another object of the present invention to provide an electrodeconstruction of the above character wherein certain of the electrodesections may be connected to power sources of different magnitudes sothat different amperages may be simultaneously applied to differentareas of a workpiece.

It is still another object of the present invention to provide a newimproved electrode construction of the above character wherein thesupport member constitutes a dielectric fluid manifold chamber.

It is a further object of the present invention to provide an electrodeconstruction wherein the support member includes a new and improvedmeans defining a reference surface upon which the segmental electrodesections may be detachably mounted.

It is a related object of the present invention to provide a supportmember with a deformable material which, when initially engaged with theelectrode sections, is deformed to a conformation defining the aforesaidreference surface.

It is a further object of the present invention to provide an electrodeconstruction of the above-described type wherein auxiliary fasteningmeans, such as screws, adhesive or the like, may be used for securingthe electrode sections upon the reference surface.

It is yet another object of the present invention to provide a new andimproved electrode construction of the above type wherein the segmentalelectrode sections may be fabricated of different electrode materials.

Another object of the present invention is to provide an electrodeconstruction of an extremely simple design which is adapted particularlyfor machining partings for tools, dies, and the like.

Other objects and advantages of the present invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevated perspectiveview of the electrode construction of the present invention, as shown inoperative association with a typical electrical discharge machine;

FIG. 2 is a side elevational view of the electrode construction shown inFIG. I, as taken in the direction of the arrow 2 therein;

FIG. 3 is a transverse cross-sectional view through the electrodeconstruction of the present invention, as seen in operative associationwith a typical workpiece;

FIG. 4 is an enlarged fragmentary view of a portion of one of thefastening means utilized in detachably securing an electrode section tothe electrode holder of the present invention;

FIG. 5 is an elevated perspective view of a typical workpiece with whichthe electrode construction of the present invention may be operativelyassociated;

FIG. 6 is a side elevational view of an alternate embodiment of theelectrode construction of the present invention;

FIG. 7 is a side elevational view of the electrode holder, electrodesupport pattern and segmental electrode sections as they would be seenprior to mounting the electrode sections on the electrode holder, and

FIG. 8 is a view similar to FIG. 7 showing the electrode holder engagedwith the segmental electrode sections during the process of transferringsaid sections to the holder and forming the permanent reference surfaceon the holder.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now in detailto the drawings, an electrode assembly 10, in accordance with apreferred embodiment of the present invention, is shown in operativeassociation with an electrical discharge machine 12 having a base orsupport structure 14 upon which an upwardly extending frame 16 isdisposed for supporting a vertically reciprocable electrode supportinghead 18. As illustrated in FIG. 1, the electrode assembly is mounted onthe lower end of the head 18 and is thereby supported for reciprocalmovement in the direction of the arrow 19. The support structure 14 alsocomprises a generally horizontally disposed machine table 20 which ismovable in a forward and rearward direction, as indicated by the arrow22. The machine table 20 supports a dielectric fluid reservoir 24whichis movable transversely of the structure 14 in the directionindicated by the arrow 26. Suitable control means such as a drive screw(not shown) operable upon rotation of a handwheel 28 may be used foreffecting movement of the table 20, while movement of the reservoir 24may be controlled through suitable movement of an additional handwheel30. The electrode supporting head 18 may be manually moved verticallywithin suitable guide means 31 on the frame 16 by means of a rack and,pinion arrangement (not shown) connected to a movable handle 32, oralternatively, may be moved automatically by a suitable electricservomechanism operable in conjunction with a conventional hydrauliccylinder 34.

In operation, a typical workpiece, generally designated herein by thenumeral 36 is placed within the reservoir 24 beneath the electrodeassembly 10. A fluid dielectric is communicated into the reservoir 24(or alternatively, into the electrode assembly 10, as will be described)through suitable conduit means 38 and 40. An electrical potential isprovided between the workpiece 36 and the electrode assembly 10 until amaterial eroding spark passes or is discharged from the assembly 10 tothe workpiece 36. A predetermined gap or spacing is maintained betweenthe side of the workpiece 36 being machined and the working surface ofthe electrode assembly 10 by moving the assembly 10 vertically relativeto the workpiece 36 by means of the head 18, whereby material will beremoved or eroded from the workpiece 36 in a manner well known in theart. it will be noted that the general structure and operation of theelectrical discharge machine 10 is well known in the art, and thereforea detailed description of the construction and operation thereof will beomitted for purposes of simplicity, since the invention described hereindeals particularly with the electrode construction 10 per se and themethod of making the same.

Generally speaking, the electrode assembly 10 comprises an electrodeholder which is adapted to be mounted upon the head 18 of the machine 12and operatively support a plurality of segmental electrode sections in amanner such that said sections may be conveniently removed from theholder and replaced when they become consumed, with the result thatafter extended use of the electrode construction 10, a major part of theassembly is reusable by merely substituting new segmental electrodesections on the working face of the electrode holder, thereby maximizingthe economies of operation. As will hereinafter be described, theelectrode sections are adapted to be secured upon a permanent referencesurface defined on the lower side of the electrode holder, which surfaceis formed upon operatively mounting the initial electrode sections inplace upon the holder, with suitable auxiliary fastening means beingemployed where necessary to detachably secure the electrode sections intheir respective operative positions.

The electrode holder is generally designated by the numeral 42 andcomprises a plurality of upstanding side sections, generally designated44, that are connected at their lower ends to a generally horizontallydisposed electrode support section 46. The sections 44, 46 cooperatewith one another to define a fluid chamber 48 into or from whichdielectric fluid may be communicated via suitable fluid fitting means 50threadably mounted within a suitable bore 52 on one of the side sections44, as best seen in FIG. 3. The fitting means 50 may be communicablethrough any suitable conduit means, for example, conduit means 38, 40,to a suitable source of dielectric fluid, as will be apparent. Theelectrode holder 42 may be fabricated of any relatively strong, rigid,electrically conductive or nonconductive material, such as any one of anumber of well-known synthetic plastic materials, or alternatively, of acomposition material such as are manufactured and distributed under thename Masonite, or other materials which are easy to fabricate so as tocreate the desired geometry of the member 42. One construction which hasbeen found to be particularly satisfactory is where the sections 44, 46are fabricated of a honeycomb structure which provides a stronglightweight construction that is extremely economical to manufacture andconvenient to assemble. In the embodiment illustrated herein, theelectrode holder 42 is fabricated of a metal casting, with the resultthat the side sections 44 and electrode support section 46 areintegrally connected to one another. In a preferred construction of thepresent invention, the electrode holder 42 may be fabricated of asuitable metal casting or of the above described honeycomb material,whichever material proves most satisfactory for a particularapplication.

As illustrated in H0. 3, the electrode section 46 comprises a pluralityof upwardly inclined or offset, integrally or otherwise connected facetportions, generally designated 54, that generally assume a configurationcorresponding to the shape of the workpiece 36 which is to beelectrically machined via the assembly 10. The lower sides of theportions 54, as seen in FIG. 7, define a plurality of surface areas,generally designated 56, which are of an initial shape generallycorresponding to the shape of the workpiece and upon which the pluralityof segmental electrode sections, hereinafter to be described, areoperatively mounted. it will be noted that the specific conformation ofthe surface areas 56 is not particularly critical, within predeterminedlimitations, with the result that the electrode support section 46 maybe fabricated by means of "rough" casting techniques, well known in theart, with the surface areas 56 not requiring any expensive precisionmachining in order to prepare said areas 56 for operative reception ofthe electrode sections, thereby minimizing the cost of manufacturing theelectrode holder 42.

The holder 42 may be secured by means of an outwardly projecting flangeportion 57 on the holder 42 and suitable screws, bolts or the like 58 toa support member 60 defining a flat horizontally extending lower surface62 against which the upper ends of the side sections 44 are abuttinglyengaged, the member 60 being secured by any suitable means upon thelower end of the head 18 of the machine 12 and serving to close theupper side of the chamber 48, as will be apparent.

The plurality of segmental electrode sections, generally designated bythe numeral 64, will be seen as being of a generally flat or planar,uniformly thick configuration and arranged or operatively mounted uponthe electrode holder 42 such that they are in generally edge abuttingrelationship, as illustrated in FIG. 3. More particularly, the electrodesections 64 are arranged such that they define a lower working surfacewhich is of the exact shape or conformation as the surface which is tobe machined upon the workpiece, such as the workpiece 36. Accordingly,the various confronting edge portions between the electrode sections 64are shaped, as by beveling, chamfering, or the like, such that the lowerside of the totality of the sections 64 presents a surface correspondingto the conformation to the workpiece. It will be apparent, of course,that any skilled artisan will readily be able to cut and properly shapethe electrode sections commensurate with the conformation of theassociated workpiece, and that the various electrode sections 64 shownand described herein are merely for purposes of illustration.

The segmental electrode sections 64 may be fabricated of any suitableelectrically conductive material, but in a preferred construction of thepresent invention, are fabricated of graphite or carbon which is bothconvenient to fabricate and economical to commercially manufacture. Whenthe electrode sections 64 are thus fabricated of graphite or carbon,said sections 64 are preferably dimensioned so as to be approximately0.25 inch in thickness which is selected as being a satisfactorycompromise between ease in manufacturing, handling and the like, andcost of the electrode material. Where certain applications so dictate,the electrode sections 64 may be fabricated of various materials otherthan graphite or carbon, such as brass, copper, tungsten-carbide, orother suitable electrically conductive material, with one particularfeature of the present invention residing in the fact that for a givenelectrode assembly I0, the electrode sections 64 may be fabricated ofdifferent materials. Such a feature will find particularly usefulapplication, for example, where it is desired to provide an electrodesection 64 which is more resistant to wear or erosion at a location onthe electrode assembly where one edge of the particular electrodesection does predominately the major part of machining a certain surfacearea on the associated workpiece. For example, in the electrode assembly10 described herein, all of the electrode sections 64 might befabricated of carbon, with the exception of the electrode section 64'and 64", which, for example, might be fabricated of tungsten-carbide.Since the electrode sections 64, 64" have the lower leading edgesthereof accomplishing a major portion of the machining on the associatedsurface areas of the workpiece 36 as the electrode assembly 10 movesvertically downwardly during a typical machining operation, and sincethe remaining of the electrode sections 64 accomplish their respectivemachining operations by exposing a major portion of their sides (insteadof edges) to the workpiece, the rate of erosion or wear of saidremaining electrode sections 64 will be somewhat less than the rate ofwear of the electrode sections 64, 64", with the result that by using aharder or more erosionresistant electrode material for the electrodesections 64', 64", and a relatively softer or erosive material for theremaining electrode sections 64, the overall rate of consumption or wearof all the electrode sections 64 will be substantially equalized so asto minimize "down time for electrode replacement.

In accordance with one of the principles of the present invention,disposed between the rearward or upper sides of the plurality ofelectrode sections 64 and the surface areas 56 defined by the portions54 of the electrode holder 42 is a layer of material, generallydesignated 68, which functions to provide or define a plurality ofgenerally planar mounting surfaces, generally designated 70,corresponding one with each of the surface areas 56 and with each of aplurality of areas or face portions 71 defined on the workpiece 36 andwhich are to be machined or formed by means of the electrode assembly10. The material 68, for purposes of convenience of description, isgenerally referred to herein as grout, but need not necessarily be aplasterlike composition as grout is commonly understood to be. Instead,the term grout, as used herein, may consist of any suitable relativelydeformable or cold flow material which may be provided on the varioussurface areas 56 and adapted to deform when engaged with the upper sidesof the electrode sections 64 so as to form and thereby define thevarious mounting surfaces 70. In a preferred construction of thepresentinvention, the grout 68 is selected from the group of thixotropicplastics, ceramics, modeling plaster or the like which may or may not beof a thermosetting character and is adapted, when placed upon thevarious surface areas 56, to make a permanent bond therewith, yet willnot permanently bond to the electrode sections 64 when engagedtherewith. As will be described in connection with the overall processof making the electrode assembly 10 of the present invention, as thegrout 68 is initially engaged with the various electrode sections 64, itdeforms or flows into a configuration defining the plurality of surfaces70, the totality of which constitute a permanent reference surface uponwhich not only the original or initial electrode sections 64 may bemounted, but which upon all additional electrode sections 64 that may besubsequently utilized as replacements for the original sections 64 maybe mounted. Therefore, the grout 68 defines on the electrode holder 42the aforesaid reference surface automatically upon the initial mountingof the electrode sections 64 thereon, which reference surface will beseen to be accurately oriented with respect to both the holder 42 andthe surface of the workpiece to be machined, since the grout 68, byvirtue of its preferred cold flow characteristics, will flow or beforced into and around the peripheral edges of the upper or rearwardsides of the electrode sections 64 upon engagement therewith. It will benoted that the grout material 68 provides a continuous bearing areaagainst or upon which the electrode sections 64 may be contiguously, andtherefore, firmly mounted with respect to the holder 42.

The plurality of electrode sections 64 are adapted to be fixedly securedto their respective surfaces 70 defined by the grout material 68 by anysuitable means which permits the sections 64 to be selectively removedin order to provide for a replacement or substitution thereof. By way ofexample, a suitable adhesive material may be used which, at normaloperative temperatures functions to positively bond the electrodesections 64 to the surfaces 70, but when the temperature of the adhesiveis elevated some predetermined amount, said adhesive material willrelease the electrode sections 64 for purposes of replacement. In theembodiment illustrated herein, however, the electrode sections 64 areadapted to be detachably secured to the surfaces 70, and hence to theelectrode holder 42, by means of suitable screws, bolts or the like,generally designated 72, which extend through suitable apertures 74 (seeFIG. 4) formed in the electrode sections 64 and are threadably receivedwithin suitable bores 76 formed in the electrode holder 42, or in somecases in the grout 68, as is the case in connection with the electrodesection 64'. In order to provide a smooth and continuous working surfaceon the lower side of the electrode sections 64 which confront andaccomplish the actual machining on the workpiece 36, the heads of thescrews, bolts or the like 72 are preferably recessed or countersunkflush with the surface of the sections 64 via suitable recesses orcounterbores 78, in a manner well known in the art, with the heads ofthe screws, bolts or the like 72, if slotted, being provided with asuitable filler means in order to further theeffort toward providing asmooth continuous surface on the electrode sections 64. By virtue of thefact that such filler means should be of an electrically conductivematerial so as to not interrupt the discharge of electrical potentialfrom the electrode assembly 10 toward the workpiece 36, one particularlysatisfactory filler means for the screw slots, herein identified by thenumeral 80, are sections of a conductive metal wire 82 of appropriatecross section to be removably received within the slots 80. It will beapparent, of course, that various alternate constructions may be usedfor filling the slots 80, and alternatively, nonslotted fastening meansmay be used instead of the screws 72 without departing from the scope ofthe present invention.

Referring now to the overall process or method of fabricating theelectrode assembly 10, in accordance with the principles of the presentinvention, initially a mold, pattern or the like is provided having ordefining a surface which is identical to the final configuration towhich the workpiece 36 is to be machined by means of the electrodeassembly 10. The pattern or mold may be provided by means of anysuitable tool, fixture or the like, and may, in some instances, compriseone of the workpieces 36 which has already been machined to its final orfinished shape. Such a pattern is illustrated in FIG. 7 and designatedby the numeral 84. The pattern 84 is shown as defining a plurality offacets or face portions, generally designated 86 which are identical insize and shape to the face portions 71 that are to be machined upon theworkpiece 36. After the pattern 84 has been properly constructed, theplurality of electrode sections 64 are produced by cutting or otherwisefabricating the sections 64 from a suitable sheet or other shape pieceof the electrode material, the electrode sections 64 having theirrespective end portions, beveled, chamfered or similarly shaped in themanner shown in FIG. 7 such that they may be operatively positioned uponthe facets 86 in a position wherein the lower sides thereof contiguouslyengage the facets 86 in the same manner as the electrode sections 64will ultimately engage the face portions 71 of the workpiece 36. Beforethe electrode sections 64 are placed upon the pattern 84 in the mannershown in FIG. 7, preferably some type of parting or release agent isprovided on the facets 86, which agent will function to properlytemporarily position the electrode sections '64 against any movementrelative to one another or relative to the pattern 84, but will permitthe electrode sections 64 to be moved away from the facets 86 when aseparating force of sufficient magnitude is exerted thereon. Thereafter,the electrode sections 64 are properly oriented upon the facets 86preparatory to their being transferred to and being mounted upon theelectrode holder 42, as will now be described.

Assuming that the electrode holder 42 is fabricated in a manner suchthat the portions 54 thereof define the plurality of surface areas 56corresponding to the facets 86 of the pattern 84, the electrode holder42 is provided with a layer of the above-described grout material 68which may be placed upon the surface areas 56 in a relatively generousmanner, as indicated in FIG. 7. After the grout 68 has been thusprovided on the surface areas 56, the electrode holder 42 is properlypositioned above the pattern 84 and electrode sections 64 supportedthereon, after which time the electrode holder 42 is biased downwardlyor in the direction of the arrow 88 in FIG. 7 from the position shown inFIG. 7 to the position shown in FIG. 8. As the electrode holder 42 isthus moved, it will be seen that the grout material 68 will be biasedinto engagement with the upper sides of the electrode sections 64mounted on the pattern 84, whereby the grout 68 will freely flow to ashape or conformation continuously engaged within the confronting orupper surfaces of the electrode sections 64 and thereby form and providethe plurality of surfaces 70 constituting the aforedescribed permanentreference surface upon which the electrode sections 64 are operativelymounted. The grout 68 is of a character such that it will sufficientlybond the electrode sections 64 to the holder 42 with a force greaterthan the force of the release or parting agent temporarily maintainingthe electrode sections 64 positioned upon the pattern 84, with theresult that when the electrode holder 42 is moved upwardly away from thepattern 84, or in the direction of the arrow 90 in FIG. 8, the electrodesection 64 will be transferred from the facets 86 of the pattern 84 tothe holder 42 preparatory to the electrodesections 64 being detachablysecured to the electrode holder 42, as above described. It will,therefore, be seen that the process of moving the electrode holder 42downwardly intofengagement with the electrode sections 64 supported uponthe pattern 84 and thereafter moving the electrode holder 42 away fromthe pattern 84 accomplishes two functions; namely, forming the permanentreference surface in the grout material 68 and hence upon the electrodeholder 42, and transferring the initial electrode sections 64 from thepattern 84 to the electrode holder 42. After this has been accomplished,the electrode section 64 may be secured in the manner above described tothe electrode holder 42 preparatory tothe assembly 10 being operativelymounted upon the machine 12.

For certain electrical discharge machining operations, in order to coolthe electrode assembly 10 and associated workpiece 36 and to convey themachined particles from the gap or spacing existing between the assembly10 and workpiece 36, it may be sufficient to merely circulate dielectricfluid within the reservoir 24; however, for other machiningapplications, it may be desired to directly communicate the dielectricfluid between the manifold chamber 48 and the gap between the assemblyl0 and workpiece 36. When this is desired, a plurality of suitable flowpassages, generally designated 92, may be formed through the holdersupport'section 46 and electrode sections 64 communicating the chamber48 with the working or lower side of the electrode sections 64. Withthis arrangement, dielectric fluid may be communicated either from thechamber 48 to the spacing between the assembly 10 and workpiece 36, andthereafter to the interior of the reservoir 24, or vice versa; theparticular direction of dielectric flow therefore being selected withwide latitude in accordance with the particular application at hand.

A particular feature of the present invention resides in the fact thatfor certain electrical discharging machining operations, an electricalinsulating space may be provided between certain of the electrodesections 64 and certain other of said sections 64 so that electricalpower of different magnitudes may be communicated to selected electrodesections 64 in order to adapt the assembly 10 for specialized machiningoperations. More particularly, a space 94 (see FIG. 6) may be providedbetween, for example, the electrode sections 64 on the right side of theassembly 10 separating said electrode sections from the sections 64 onthe left side of the assembly 10. With this arrangement, a greater orhigher amperage may be communicated to one side of the assembly 10 thanthe other side thereof so that different rates of machining may beaccomplished simultaneously by different areas of the electrode assembly10. it will be noted that when the aforesaid spacing 94 is providedbetween the peripheral edges of one or more of the electrode sections 64in order to permit the application of a greater or smaller amperagethereto, said spacing 94 may be used to communicate dielectric fluidfrom a suitable opening in the associated electrode holder section 46 sothat dielectric fluid may be communicated between the electrode sections64 and the manifold chamber 48 via the spacing 94.

Due to the end abutting relationship between the various electrodesections 64, an electrical potential connected to one end thereof willbe communicated through the electrode sections 64 to the others thereof,except, however, in the event a gap or spacing is provided betweencertain of the electrodes for the reasons stated above. If for anyreason a more positive electrical communication is desired between thevarious electrode sections 64, or for situations wherein theconfiguration of the workpiece necessitates that certain of theelectrodes 64 be isolated from others thereof, the assembly 10 may beprovided with auxiliary electrical conductors (see H6. 2) 96 whichextend between the electrode sections 64 and are connected thereto bysuitable terminal means 98. It will be apparent, of course, that theauxiliary conductors 96 should extend around the outer periphery of theassembly 10 so as to not impair the effectiveness of the electrodesections 64 during an electrical discharge machining operation.

it will be noted that although in the embodiments of the electrodeassembly 10 of the present invention illustrated herein, the variouselectrode sections 64 are arranged so as to define a working surfaceconsisting of a plurality of generally flat or planar surface areas, thepresent invention, as defined herein, is not intended to exclude aconstruction wherein the working surface of the electrode sections 64are of a relatively arcuate or curvilinear configuration. That is, it iscontemplated that the various electrode sections utilized in theelectrode assembly 10 may define curved working surfaces or may bedesigned such that a plurality thereof lie along the tangent of a curvedsurface and are thereby adapted to effect a machining operation on arelatively arcuate shaped surface of an associated workpiece. Such aconstruction, as will be apparent, might consist of a plurality ofrectangularly, triangu larly or other shaped electrode sections arrangedupon the electrode holder 42 in a manner above described. Accordingly,the present invention will not only find application in machiningworkpieces having a series of flat or planar facets or surface areas,but also may be used in machining workpieces having curved or arcuatesurface areas.

It will be seen from the above that the present invention provides a newand improved electrical discharge machining electrode assembly andmethod of making same which embodies a number of particularly importantfeatures not shown in similar devices of the prior art. One particularlyimportant feature resides in the novel means of providing a permanentreference surface upon which the electrode sections 64 are mounted,which surface permits successive electrode sections to be mountedthereon as they become consumed and serves to automatically and properlyorient each electrode section 64 with respect to the correspondingsections without the need for any precision machining or other expensivefabricating techniques. Another particularly important feature of thepresent invention resides in the fact that different electrode materialsmay be used simultaneously, and that where desired, different electricalpotentials may be supplied to different areas of the assembly 10,thereby providing for universality of application. Still another featureof the present invention resides in the provision of the dielectricmanifold chamber defined within the electrode holder 42 which permitsdielectric fluid to be transmitted directly to the space between theassembly and its associated workpieces. .Yet another feature of thepresent invention resides in the fact that as the electrode sections 64become worn, they may be removed and provided with a suitable shim orother structural member which acts to advance the lower or working facethereof downwardly to some preselected position relative to theassociated of the electrode sections 64, thereby providing for continueduse of an electrode section 64 even though it has become somewhat erodedor worn, and thus effectively extend the operational life thereof.

While it will be apparent that the preferred embodiments illustratedherein are well calculated to fulfill the objects above stated, it willbe appreciated that the present invention is susceptible tomodification, variation and change without departing from the scope ofthe invention.

lclaim:

1. ln an electrical discharge electrode for machining a relativelynonplanar surface on a workpiece,

a body member defining a relatively irregular mounting surface roughlyapproximating the contour of surface to be machined on the workpiece,

a plurality of segmental electrode elements having front and rear sidesmounted on said body member, said irregular mounting surface and saidplurality of electrode elements together defining spaces,

said elements being arranged in generally edge-to-edge abuttingrelationship and together defining a machining surface substantiallycomplementary to the surface to be machined on the workpiece, and

a layer of material substantially filling the spaces between therearward sides of said elements and said irregular mounting surface andadapted to have said elements contiguously engaged therewith.

2. The invention as set forth in claim 1 wherein said material betweensaid body member and said electrode elements is bonded to said bodymember and is detachably engaged with said electrode sections. I

3. The invention as set forth in claim 1 wherein said material betweensaid body member and said electrode elements has preselected flowproperties such that a reference surface is formed when said body memberis urged to engagement with said electrode elements.

4. The invention as set forth in claim 3 wherein said material isselected from the group of thixotropic plastics, ceramics and plaster.

5. The invention as set forth in claim 1 which includes means fordetachably securing said electrode elements to said body member, saidsecuring means comprising screw means extending through said electrodeelements and threadably engaged with said body member.

6. The invention as set forth in claim 5 wherein said screw meanscomprise slotted head sections which are recessed below the surface ofsaid electrode elements, and wherein the slots of said screws areadapted to receive a suitable filler means.

7. The invention as set forth in claim 1 which includes means fordetachably securing said electrode elements to said body member, saidsecuring means comprising an adhesive material.

8. The invention as set forth in claim 1 wherein said body memberincludes means defining a dielectric fluid manifold chamber.

9. The invention as set forth in claim 8 which includes passage meansextending between said chamber and machining surface of said electrodeelements for communicating dielectric fluid therebetween.

l0. The invention as set forth in claim 1 wherein some of said electrodeelements are abuttingly engageable with one another and are therebyadapted to complete an electrical circuit between one another and otherofsaid elements are disengaged with certain of said elements so as to beelectrically isolated from said certain elements.

11. The invention as set forth in claim 10 which includes auxiliaryconductor means for completing an electrical circuit between some ofsaid electrode elements.

12. The invention as set forth in claim 1 wherein the marginal edge ofone of said electrode elements is spaced away from the marginal edge ofthe adjacent of said electrode elements for electrically insulating saidone section from the other of said sections.

13. The invention as set forth in claim 11 wherein said electrodeelements are adapted to be connected to a power source via first andsecond electrical power circuit means for communicating electricalenergy to said some of said electrode elements and said isolatedelements, respectively, whereby electrical energy of differentmagnitudes may be communicated to said electrode elements.

14. The invention as set forth in claim 12 wherein the marginal edges ofsaid one electrode elements and the marginal edges of said otherelectrode elements define a recessed gap, and which includes means forcommunicating dielectric fluid from a source thereof through said gap.

15. The invention as set forth in claim 1 wherein said electrodeelements are fabricated of different materials so as to be consumed atdifferent rates during operation of the associated electrical dischargemachine.

16. The invention as set forth in claim 12 wherein at least one of saidelectrode elements is oriented generally parallel to the direction ofmovement of the electrode, said one electrode element being fabricatedof a more wear resistant material than the other of said electrodeelements.

17. The invention as set forth in claim 1 wherein said body memberdefines a multiple faceted mounting surface, and which includes at leastone electrode element adapted to be detachably secured to each of thefacets of said mounting surface.

18. In an electrical discharge electrode movable toward and away from aworkpiece for machining a relatively nonplanar surface thereon,

a body member defining a relatively irregular mounting sur face roughlyapproximating the contour of surface to be machined on the workpiece,

a plurality of generally flat, uniform thickness segmental electrodeelements having front and rear sides mounted on said body member, saidirregular mounting surface and said plurality of electrode elementstogether defining spaces,

said elements being arranged in generally edge-to-edge abuttingrelationship and together defining a machining surface complementary tothe surface to be machined on the workpiece, and

a layer of material substantially filling the spaces between therearward sides of said elements and said irregular mounting surface andadapted to have said elements contiguously engaged therewith,

at least one of said electrode elements being generally coplanar withthe direction of movement of the electrode toward and away from theworkpiece, with said one electrode element being fabricated of electrodematerial having increased wear resistance as compared to other of saidelectrode elements,

19. In an electrical discharge electrode for machining a relativelynonplanar surface on a workpiece,

a body member defining a relatively irregular mounting surface roughlyapproximating the contour of surface to be machined on the workpiece,

a plurality of segmental electrode elements having front and rear sidesmounted on said body member, said irregular mounting surface and saidplurality of electrode elements together defining spaces,

said elements being arranged in generally edge-to-edge abuttingrelationship and together defining a machining surface complementary tothe surface to be machined on the workpiece, and

a layer of material substantially filling the spaces between therearward sides of said elements and said irregular mounting surface andadapted to have said elements contiguously engaged therewith,

at least some of said electrode elements being fabricated of differentelectrode materials, whereby said electrode elements will be consumed atdifferent rates during a machining operation.

20. In an electrical discharge machine including first and second powersources,

an electrode for machining a relatively nonplanar surface on aworkpiece, said electrode comprising,

a body member defining a relatively irregular mounting surface roughlyapproximating the contour of surface to be machined on the workpiece,

a plurality of generally flat, uniform thickness segmental electrodeelements having front and rear sides mounted on said body member, saidirregular mounting surface and said plurality of electrode elementstogether defining spaces,

said elements being arranged in generally edge-to-edge abuttingrelationship and together defining a machining surface complementary tothe surface to be machined on the workpiece,

a layer of material substantially filling the spaces between therearward sides of said elements and said irregular mounting surface andadapted to have said elements contiguously engaged therewith, I

at least one of said electrode elements being electrically insulatedfrom other of said electrode elements, and

first circuit means connecting said insulated element to said firstpower source and second circuit means for connecting other of saidelectrode elements to said second power source.

21. In an electrical discharge electrode for machining a relativelynonplanar surface on a workpiece,

a body member defining a relatively irregular mounting surface roughlyapproximating the contour of surface to be machined on the workpiece,

a plurality of generally flat, uniform thickness segmental electrodeelements having front and rear sides mounted on said body member, saidirregular mounting surface and said plurality of electrode elementstogether defining spaces,

said elements being arranged in generally edge-to-edge abuttingrelationship and together defining a machining surface complementary tothe surface to be machined on the workpiece, and

a layer of material substantially filling the spaces between therearward sides of said elements and said irregular mounting surface andadapted to have said elements contiguously engaged therewith,

the edges of at least some of said electrode elements being coplanarwith one of the sidesof adjacent of said electrode elements, whereby toprovide a substantially continuous machining surface complementary tothe surface to be machined on the work iece. 22. In an electricaldischarge e ectrode for machining a relatively nonplanar surface on aworkpiece,

a body member defining a relatively irregular mounting surface roughlyapproximating the contour of surface to be machined on the workpiece,

a plurality of generally flat, uniform thickness segmental electrodeelements having front and rear sides mounted on said body member, saidirregular mountingsurface and said plurality of electrode elementstogether defining spaces,

said elements being arranged in generally edge-to-edge abuttingrelationship and together defining a machining surface complementary tothe surface to be machined on the workpiece, and

a layer of material substantially filling the spaces between therearward sides of said elements and said irregular mounting surface andadapted to have said elements contiguously engaged therewith, I

said material being of a generally thixotropic character and therebybeing initially deformable upon engagement of said electrode elementstherewith and upon curing thereof defining the permanent surface uponwhich said electrode elements may be detachably secured.

1. In an electrical discharge electrode for machining a relativelynonplanar surface on a workpiece, a body member defining a relativelyirregular mounting surface roughly approximating the contour of surfaceto be machined on the workpiece, a plurality of segmental electrodeelements having front and rear sides mounted on said body member, saidirregular mounting surface and said plurality of electrode elementstogether defining spaces, said elements being arranged in generallyedge-to-edge abutting relationship and together defining a machiningsurface substantially complementary to the surface to be machined on theworkpiece, and a layer of material substantially filling the spacesbetween the rearward sides of said elements and said irregular mountingsurface and adapted to have said elements contiguously engagedtherewith.
 2. The invention as set forth in claim 1 wherein saidmaterial between said body member and said electrode elements is bondedto said body member and is detachably engaged with said electrodesections.
 3. The invention as set forth in claim 1 wherein said materialbetween said body member and said electrode elements has preselectedflow properties such that a reference surface is formed when said bodymember is urged to engagement with said electrode elements.
 4. Theinvention as set forth in claim 3 wherein said material is selected fromthe group of thixotropic plastics, ceramics and plaster.
 5. Theinvention as set forth in claim 1 which includes means for detachablysecuring said electrode elements to said body member, said securingmeans comprising screw means extending through said electrode elementsand threadably engaged with said body member.
 6. The invention as setforth in claim 5 wherein said screw means comprise slotted head sectionswhich are recessed below the surface of said electrode elements, andwherein the slots of said screws are adapted to receive a suitablefiller means.
 7. The invention as set forth in claim 1 which includesmeans for detachably securing said electrode elements to said bodymember, said securing means comprising an adhesive material.
 8. Theinvention as set forth in claim 1 wherein said body member includesmeans defining a dielectric fluid manifold chamber.
 9. The invention asset forth in claim 8 which includes passage means extending between saidchamber and machining surface of said electrode elements forcommunicating dielectric fluid therebetween.
 10. The invention as setforth in claim 1 wherein some of said electrode elements are abuttinglyengageable with one another and are thereby adapted to compleTe anelectrical circuit between one another and other of said elements aredisengaged with certain of said elements so as to be electricallyisolated from said certain elements.
 11. The invention as set forth inclaim 10 which includes auxiliary conductor means for completing anelectrical circuit between some of said electrode elements.
 12. Theinvention as set forth in claim 1 wherein the marginal edge of one ofsaid electrode elements is spaced away from the marginal edge of theadjacent of said electrode elements for electrically insulating said onesection from the other of said sections.
 13. The invention as set forthin claim 11 wherein said electrode elements are adapted to be connectedto a power source via first and second electrical power circuit meansfor communicating electrical energy to said some of said electrodeelements and said isolated elements, respectively, whereby electricalenergy of different magnitudes may be communicated to said electrodeelements.
 14. The invention as set forth in claim 12 wherein themarginal edges of said one electrode elements and the marginal edges ofsaid other electrode elements define a recessed gap, and which includesmeans for communicating dielectric fluid from a source thereof throughsaid gap.
 15. The invention as set forth in claim 1 wherein saidelectrode elements are fabricated of different materials so as to beconsumed at different rates during operation of the associatedelectrical discharge machine.
 16. The invention as set forth in claim 12wherein at least one of said electrode elements is oriented generallyparallel to the direction of movement of the electrode, said oneelectrode element being fabricated of a more wear resistant materialthan the other of said electrode elements.
 17. The invention as setforth in claim 1 wherein said body member defines a multiple facetedmounting surface, and which includes at least one electrode elementadapted to be detachably secured to each of the facets of said mountingsurface.
 18. In an electrical discharge electrode movable toward andaway from a workpiece for machining a relatively nonplanar surfacethereon, a body member defining a relatively irregular mounting surfaceroughly approximating the contour of surface to be machined on theworkpiece, a plurality of generally flat, uniform thickness segmentalelectrode elements having front and rear sides mounted on said bodymember, said irregular mounting surface and said plurality of electrodeelements together defining spaces, said elements being arranged ingenerally edge-to-edge abutting relationship and together defining amachining surface complementary to the surface to be machined on theworkpiece, and a layer of material substantially filling the spacesbetween the rearward sides of said elements and said irregular mountingsurface and adapted to have said elements contiguously engagedtherewith, at least one of said electrode elements being generallycoplanar with the direction of movement of the electrode toward and awayfrom the workpiece, with said one electrode element being fabricated ofelectrode material having increased wear resistance as compared to otherof said electrode elements.
 19. In an electrical discharge electrode formachining a relatively nonplanar surface on a workpiece, a body memberdefining a relatively irregular mounting surface roughly approximatingthe contour of surface to be machined on the workpiece, a plurality ofsegmental electrode elements having front and rear sides mounted on saidbody member, said irregular mounting surface and said plurality ofelectrode elements together defining spaces, said elements beingarranged in generally edge-to-edge abutting relationship and togetherdefining a machining surface complementary to the surface to be machinedon the workpiece, and a layer of material substantially filling thespaces between the rearward sides of said elements and said irregularmounting surface and adapted to have said elements contiguously engagedtherewith, at least some of said electrode elements being fabricated ofdifferent electrode materials, whereby said electrode elements will beconsumed at different rates during a machining operation.
 20. In anelectrical discharge machine including first and second power sources,an electrode for machining a relatively nonplanar surface on aworkpiece, said electrode comprising, a body member defining arelatively irregular mounting surface roughly approximating the contourof surface to be machined on the workpiece, a plurality of generallyflat, uniform thickness segmental electrode elements having front andrear sides mounted on said body member, said irregular mounting surfaceand said plurality of electrode elements together defining spaces, saidelements being arranged in generally edge-to-edge abutting relationshipand together defining a machining surface complementary to the surfaceto be machined on the workpiece, a layer of material substantiallyfilling the spaces between the rearward sides of said elements and saidirregular mounting surface and adapted to have said elementscontiguously engaged therewith, at least one of said electrode elementsbeing electrically insulated from other of said electrode elements, andfirst circuit means connecting said insulated element to said firstpower source and second circuit means for connecting other of saidelectrode elements to said second power source.
 21. In an electricaldischarge electrode for machining a relatively nonplanar surface on aworkpiece, a body member defining a relatively irregular mountingsurface roughly approximating the contour of surface to be machined onthe workpiece, a plurality of generally flat, uniform thicknesssegmental electrode elements having front and rear sides mounted on saidbody member, said irregular mounting surface and said plurality ofelectrode elements together defining spaces, said elements beingarranged in generally edge-to-edge abutting relationship and togetherdefining a machining surface complementary to the surface to be machinedon the workpiece, and a layer of material substantially filling thespaces between the rearward sides of said elements and said irregularmounting surface and adapted to have said elements contiguously engagedtherewith, the edges of at least some of said electrode elements beingcoplanar with one of the sides of adjacent of said electrode elements,whereby to provide a substantially continuous machining surfacecomplementary to the surface to be machined on the workpiece.
 22. In anelectrical discharge electrode for machining a relatively nonplanarsurface on a workpiece, a body member defining a relatively irregularmounting surface roughly approximating the contour of surface to bemachined on the workpiece, a plurality of generally flat, uniformthickness segmental electrode elements having front and rear sidesmounted on said body member, said irregular mounting surface and saidplurality of electrode elements together defining spaces, said elementsbeing arranged in generally edge-to-edge abutting relationship andtogether defining a machining surface complementary to the surface to bemachined on the workpiece, and a layer of material substantially fillingthe spaces between the rearward sides of said elements and saidirregular mounting surface and adapted to have said elementscontiguously engaged therewith, said material being of a generallythixotropic character and thereby being initially deformable uponengagement of said electrode elements therewith and upon curing thereofdefining the permanent surface upon which said electrode elements may bedetachably secured.